Fluid flow delivery systems which incorporate constant speed pumps are known. Such pump systems have the advantage that constant speed pumps tend to be less expensive than variable speed pump systems. On the other hand, constant speed pump systems have higher operating costs due among other reasons to utility and maintenance expenses resulting from constant operation. Additionally, there is a need to bypass or choke the discharge flow of the pumps in low demand situations. Such structures however waste energy and create unwanted heat.
Variable speed pump systems offer higher operating flexibility than do constant speed pump systems. However, known variable speed systems tend to be more expensive than known constant speed systems.
It would be desirable to be able to merge a variable speed drive with pumps that can be operated on either a constant or a variable speed basis so as to obtain the benefits of both types of systems. Preferably such a merger could be accomplished while at the same time minimizing the effects of the disadvantages of either type. It would be preferable to be able to combine the variable speed drive with constant speed pumps in a transparent fashion so as to cost effectively provide constant output pressure in response to widely varying demands.